Abstract
Background
In recent years only few novel drugs targeting visceral pain have been developed. This lack of success may be explained by animal models having poor predictive value. To increase the success of translating results from animals to humans there is a demand for comparable test models. The aim was to establish a comparable and reliable translational model to evoke mechanical rectal pain in rats and humans.
Methods
Mechanical rectal rapid balloon distension was done on two different days in 12 rats (separated by 24.3 ± 7.1 days) and 18 humans (separated by 9.3 ± 1.3 days). Evoked potentials were recorded from permanently implanted skull-electrodes in rats, at stimulation pressure of 80 mmHg and duration of 100 ms. In human surface electrodes and individualized pressure, corresponding to the pain detection threshold, lasting 150 ms, were used. Within- and between days reproducibility were assessed in terms of latencies, amplitudes and frequency content.
Results
In both rats and humans evoked potentials with tri-phasic morphology were recorded. No differences in latencies, amplitudes and power distribution were seen within or between days (all F ≤ 2.0; all P ≥ 0.2). The analyses of the EPs revealed peak-to-peak amplitude as the most reproducible parameter within (ICC ≥ 0.84) and between (ICC ≥ 0.70) days, seen across both species. The spectral analyses showed that the EEG power was distributed mainly in the delta and theta bands. The main power in rats was contained in the theta band (45%), whereas humans had the predominant power in the delta band (46%).
Conclusion
A unique visceral translational platform was established to reliably assess neurophysiologic response to rapid balloon distension in rats and humans. The model provides an approach to study basic and clinical pain as well as pharmacological intervention.
© 2012 Scandinavian Association for the Study of Pain
